content: /*
   * Copyright 2010 Aalto University, ComNet
   * Released under GPLv3. See LICENSE.txt for details.
   */
  package core;
  
  import routing.MessageRouter;
  
  /**
   * A connection between two DTN nodes.  The transmission speed
   * is updated every round from the end point transmission speeds
   */
  public class VBRConnection extends Connection {
  	private int msgsize;
  	private int msgsent;
  	private int currentspeed = 0;
  	private double lastUpdate = 0;
  
  
  	/**
  	 * Creates a new connection between nodes and sets the connection
  	 * state to "up".
  	 * @param fromNode The node that initiated the connection
  	 * @param fromInterface The interface that initiated the connection
  	 * @param toNode The node in the other side of the connection
  	 * @param toInterface The interface in the other side of the connection
  	 */
     public VBRConnection(DTNHost fromNode, NetworkInterface fromInterface,
  		   DTNHost toNode, NetworkInterface toInterface) {
  	    super(fromNode, fromInterface, toNode, toInterface);
  		this.msgsent = 0;
  	}
  
  	/**
  	 * Sets a message that this connection is currently transferring. If message
  	 * passing is controlled by external events, this method is not needed
  	 * (but then e.g. {@link #finalizeTransfer()} and
  	 * {@link #isMessageTransferred()} will not work either). Only a one message
  	 * at a time can be transferred using one connection.
  	 * @param from The host sending the message
  	 * @param m The message
  	 * @return The value returned by
  	 * {@link MessageRouter#receiveMessage(Message, DTNHost)}
  	 */
  	public int startTransfer(DTNHost from, Message m) {
  		assert this.msgOnFly == null : "Already transferring " +
  			this.msgOnFly + " from " + this.msgFromNode + " to " +
  			this.getOtherNode(this.msgFromNode) + ". Can't "+
  			"start transfer of " + m + " from " + from;
  
  		this.msgFromNode = from;
  		Message newMessage = m.replicate();
  		int retVal = getOtherNode(from).receiveMessage(newMessage, from);
  
  		if (retVal == MessageRouter.RCV_OK) {
  			this.msgOnFly = newMessage;
  			this.msgsize = m.getSize();
  			this.msgsent = 0;
  		}
  
  		return retVal;
  	}
  
  	/**
  	 * Calculate the current transmission speed from the information
  	 * given by the interfaces, and calculate the missing data amount.
  	 *
  	 */
  	public void update() {
  		currentspeed =  this.fromInterface.getTransmitSpeed(toInterface);
  		int othspeed =  this.toInterface.getTransmitSpeed(fromInterface);
  		double now = core.SimClock.getTime();
  
  		if (othspeed < currentspeed) {
  			currentspeed = othspeed;
  		}
  
  
  		msgsent += currentspeed * (now - this.lastUpdate);
  		this.lastUpdate = now;
  	}
  
  	/**
  	 * returns the current speed of the connection
  	 */
  	public double getSpeed() {
  		return this.currentspeed;
  	}
  
      /**
       * Returns the amount of bytes to be transferred before ongoing transfer
       * is ready or 0 if there's no ongoing transfer or it has finished
       * already
       * @return the amount of bytes to be transferred
       */
      public int getRemainingByteCount() {
  	int bytesLeft = msgsize - msgsent;
  	return (bytesLeft > 0 ? bytesLeft : 0);
      }
  
  	/**
  	 * Returns true if the current message transfer is done.
  	 * @return True if the transfer is done, false if not
  	 */
  	public boolean isMessageTransferred() {
  		if (msgsent >= msgsize) {
  			return true;
  		} else {
  			return false;
  		}
  	}
  
  }
  